Tourniquet Use and Local Tissue Concentrations of Cefazolin During Total Knee Arthroplasty

Key Points Question What is the effect of tourniquet application on local tissue concentration of cefazolin during total knee arthroplasty? Findings In this randomized clinical trial of 59 adults, the use of a tourniquet resulted in significantly lower concentrations in fat, synovium, and bone by 60 minutes after cefazolin infusion. The mean concentration of cefazolin measured in the local tissues ranged from 9.9 to 21.8 μg/g for the tourniquet group and was insufficient to adequately cover pathogens with elevated minimum inhibitory concentration. Meaning The study underscores the adverse effect of tourniquet inflation on tissue concentration of antibiotics and raises questions regarding cefazolin’s effectiveness against pathogens with higher minimum inhibitory concentrations.


BACKGROUND AND SIGNIFICANCE
In Canada, over 130 000 cases of primary joint arthroplasty are performed annually, and this number is increasing steadily with the aging population. (1)Projections from the United States estimate that, by 2030, more than 3.5 million primary joint arthroplasties will be performed annually. (2)Although rare, with reported rates of 0.5-2% within 2 years, periprosthetic joint infection (PJI) is a devastating complication with serious morbidity. (3)Effective use of antibiotic prophylaxis remains an important measure to prevent progression of an intraoperative contamination of the surgical site to an overt clinical infection. (4)It creates a hostile environment in blood and tissue inhibiting pathogens that could contaminate the wound throughout the procedure. (5)In order to be effective, the concentration of antibiotic must exceed the minimum inhibitory concentration (MIC) of the organism between skin incision and wound closure . (6,7) . aureus and Coagulase-negative staphylocci (CoNS), including S.epidermidis, cause close to half of deep infections and reported MIC ranges from 0.5 to 8 ug/ml in bone .(5,8,9) Achieving fourfold MIC in tissue is recommended for halting the pathogen (10) Cefazolin, efficient against most common pathogens in orthopaedics, has a good tissue penetration, minimal toxicity, low cost, and therefore is the antibiotic of choice in arthroplasty procedures (3,5) Pharmacokinetics studies have showed that Cefazolin achieves peak bone concentrations 40 minutes after parenteral application and based on systemic dosage methods, guidelines recommend that the antibiotic should be infused within 60 minutes before surgical incision.(3,(11)(12)(13) Compared to conventional systemic dosing, modern techniques using liquid chromatography and mass spectrometry can adequately measure antibiotic concentration in tissue like fat and bone.(14,15) Tourniquet inflation during total knee arthroplasty (TKA) is commonly used to reduce bleeding in the surgical field; thereby facilitating exposure and cementation.
However, reducing circulation to the leg may also reduce antibiotic distribution to the peri-incisional tissues.Once inflated, further parenteral addition of antibiotics is not likely to achieve peak concentration.Some studies propose techniques of regional prophylaxis with a tourniquet to achieve higher cefazolin tissue concentrations. (8)To our knowledge, the effect of tourniquet application on antibiotic tissue concentrations during total knee arthroplasty has not been explored.Furthermore, the effect of time from dose to incision, patient weight, and length of surgery on local tissue concentrations of Ancef are poorly understood.Considering that infections remain the leading source of early reoperation and revision surgery, insight and optimization of local tissue antibiotics is of paramount interest.
This study looks at patients who have been referred to our clinic for a potential TKA.
Once it has been determined that the patient requires a knee replacement and the patient is placed on our surgical waitlist, the patient will be asked if he or she would like to participate in the study.This randomized controlled trial would include collecting standard preoperative information, agreeing with autologous tissue collection, providing informed consent to the randomization and proceeding with standard post-operative follow-up.

OBJECTIVES, HYPOTHESIS AND STUDY QUESTIONS
The primary outcome of this study is to determine the local tissue concentrations of Cefazolin in serum, fat and bone during a primary TKA.The intervention in this study will be the application of a tourniquet or no tourniquet during the procedure.
Secondary outcomes include: time from dose to incision, patient weight, and length of surgery on local tissue concentrations.We hypothesize that application of tourniquet will limit peak concentration of Cefazolin, while prolonging its elimination.We also think that an infusion from 10-60 minutes will be equivalent in antibiotic distribution throughout the surgery and that severe obesity significantly affects Cefazolin tissue concentration.

Risks and Benefits
This research does not involve any change in the standard of care for treating this condition.Both treatment groups are well documented, acceptable standards of clinical practice and participants will not be exposed to any additional risk other than what is routinely done during a total knee arthroplasty.This trial does not involve any new experimental treatment methods.

Study Design
This will be a prospective, single centre randomized controlled trial to study patients presenting at the Montreal General Hospital for TKA.Cefazolin quantification methods will be conducted by the Goodman Cancer Research Centre Metabolomics Facility.

Study Population
Adults who require a primary total knee replacement.

Inclusion/exclusion Criteria
Inclusion Criteria: • Adults ages 18-85 who require a primary total knee replacement

• Any gender
• Osteoarthritis, rheumatoid arthritis, avascular necrosis Exclusion Criteria: • Severe allergy to antibiotic used in the study • Severe renal dysfunction (eGFR < 30 ml/min) • MRSA colonization • Patients who require revision surgery

Sample size
50 patientsproviding approximately 25 patients in each arm of randomization.
Sample size was calculated for a double-sided test with an alpha of 5%, Power of 90%, predicted difference of 25% (5 ug/g) between group and an expected standard deviation of 5 ug/g in the tissue concentration measurement based on previous studies.(7, 8, 16)

Subject recruitment, enrolment and consent process
Patients who are identified as needing a total knee replacement will be asked if they would like to participate in a study looking at antibiotic concentration throughout their surgery.If the patient agrees, the Research Assistant then will explain the study to the patients and obtain consent.

Randomization
A randomized number generator will be used to create a 1:1 allocation scheme for randomization of the patient into one of the two treatment groups.An online randomization system will be employed to deliver the treatment group and provide a sequential study identification number.Allocations will be placed in numbered, opaque, sealed envelopes.Patients will be randomized to either the tourniquet inflation group or the no tourniquet group in the preoperative area to allow appropriate setup in the operative room.

Sample collection
Once the patient has consented to the study and has agreed to continue, standard preoperative assessment will be conducted until the day of the surgery and randomization.The participation in this study will not affect the patients surgical date or eligibility for surgery.After the randomization described previously, the surgical team will conduct standard perioperative procedures.Patients will be given 2 g of Cefazolin (3g if >120 kg) systemically through a forearm vein.Time of infusion will be noted and a running timer will be started from that point.The infusion will need to be completed at least 10 minutes before inflation or skin incision.Time of tourniquet inflation, if applicable, and skin incision will be noted.A first sample of serum and fat will be obtained right after skin incision.An alarm will ring every 20 minutes from the time of Ancef administration on the recurring basis to obtain samples (Serum, Fat & Bone).Sample of subcutaneous fat and cancellous bone should measure at least 0.5 cm 2 , using a curette in the distal femur to harvest cancellous bone.Time of definitive implants insertion will also be noted.Finally, a serum sample will be obtained one to two hours after the surgery.
After the samples have been collected, they will be labeled with a randomization number, any personal information relating to the patient will be removed.After surgery, the tissue that was collected will be sent to the Goodman Cancer Research Centre for analysis.

Sample manipulation
A pilot study will be carried by the metabolomics facility for the extraction and liquid chromatography technique on mice samples with known concentrations of cefazolin.
Then, for the present study, blood and fat sample will be rinsed with normal saline solution to remove excess of blood.Sample will be stored before undergoing analysis.

Blood sample will be centrifuged and prepared to adequately dose Total & Free
Cefazolin in plasma.Bone and fat samples will be finely cut with a scalpel, placed in a buffer solution, centrifuged and prepared to measured Total adipose, Interstitial adipose and bone tissue concentration.

Blinding
Tissue concentrations of Cefazolin being the measured outcomes, blinding will not affect validity of the results.

Statistics analysis plan
Means, standard deviations, and the 95% confidence intervals will be calculated for the cefazolin concentrations in the different samples.We will execute Student T-Test and Analysis of variance for repeated measures of Cefazolin concentration between groups while adjusting for by Age, BMI, length of the surgical procedure and other parameters like blood loss and fluid resuscitation.Chi-squared test for categorical data will also be performed.

End Points
Expected timeframe is 12-24 months for data collection, analysis and manuscript preparation

MANAGEMENT AND ADMINISTRATION
The Principle Investigator and Co-Investigators are responsible for the management of this study.Authorization, user access and user rights will be assigned by the Principle Investigator and Co-Investigators to their delegates.All persons working in a clinical setting and accessing patient data will be required to have RI-MUHC research privileges and will be trained in both Good Clinical Practice (GCP) and the RI-MUHC Standard Operating Procedures (SOPs)

Data Collected
We will collect a medical history, current and past surgical information, gender, age, BMI, diagnosis for surgery and any other information that may be pertinent.We will also collect data during the procedure: randomization group, ASA score, time of antibiotic infusion, time of tourniquet inflation and deflation, time associated will all the tissue sampling, length of the procedure, blood loss and fluid resuscitation requirements.Post-operative data collection including adverse effect to the antibiotics, post-operative wound complication and clinical visit information will also be recorded.This information will be collected and kept in a secure double locked location.The information collected will only be accessible to research personnel authorized by the Principle Investigator and Co-Investigators.

Data Retention
Data related to the patient will be kept for up to 7 years as per REB requirements.If after 7 years, it is decided to keep the information longer, the data will be made anonymous.If after 7 years identifiable information is still required, every effort will be made to contact the patient and re-consent them.

CONFIDENTIALITY AND SECURITY
Only members authorized by the Principle Investigator and Co-Investigators will have access to the information.All personal and health information that is collected will remain confidential and secure to the extent permitted by applicable laws.

Adverse Events
No adverse events are expected in this study.Any adverse events will be reported as per the MUHC/Research Institute policies.

Disseminating Results
Results and findings will be communicated through group meetings, oral presentations, resident teachings and journal publications.The subjects' personal information will never be linked to any of the scientific data in question.

Withdrawal of a Participant
If a patient decides to withdraw their consent/assent, all data collected up to that point will be deleted and will not be used.

Publication
Findings from studies resulting from the information we gathered may be published: however, the participants' names will not be used in any publication.Should the results of this study be used for one or more publications, the collaborators must acknowledge the McGill Arthroplasty Group in said publication.

Intellectual Property and Commercial Uses
Any business surrounding the intellectual property of commercial use will fall under the "McGill Patents and Intellectual Property Policy".